A common type of trailer hitch provides a receiver tube attached to the back end of a motor vehicle frame or chassis below the bumper. A drawbar is inserted into the receiver tube and is retained therein by a pin passing through the sides of the receiver tube and the drawbar. The pin is retained by a cotter pin or other means. The drawbar can have a ball for towing a trailer, or it may support an accessory such as a bicycle carrier. The pin retains the drawbar in the receiver, but it does not remove play between the drawbar and the receiver tube. An accessory such as a bike carrier attached to the drawbar can force a user to reach around, under, or through the accessory, to insert the pin in an awkward body position.
The present inventor has invented prior mechanisms for tightening a drawbar in a receiver tube by turning a bolt or lever at the back end of the drawbar. Some of these are disclosed in patent documents listed in the Information Disclosure Statement. Another mechanism he invented and sold in 2008 but did not patent is shown in prior art figures herein.